Essentially, a starter unit comprises an electric motor and an electromagnetic actuator, the axes of rotation and actuation (respectively) of which are parallel to each other. The motor and actuator are secured on a starter frame, or chassis, which includes at least one so-called starter nose. The starter nose is in the form of a hood which envelops, firstly, the outer end of the output member or ram of the electromagnetic actuator, which is arranged to move in forward and backward axial motion, and secondly, the free end of the output or armature shaft of the motor. This motor shaft carries a so-called Bendix gear or pinion. The starter unit also includes an actuating lever which controls the axial movements of the Bendix gear, and which is mounted for pivoting movement about a geometrical axis which is substantially at right angles to the axes of the motor and of the electromagnetic actuator. One end of the actuating lever is coupled to the output member of the electromagnetic actuator, while its other end is in the form of a fork which acts on a thrust ring of the Bendix gear or pinion.
Examples of various designs of such a type of starter are for example illustrated in the specification of French published patent application FR 2 673 247A, in which the frame of the starter unit includes a transverse plate element which lies in a plane at right angles to the axes of the actuator and motor. The frame also includes a starter nose. In that arrangement, the actuating lever is made as a single component, the central portion of which has an articulating or pivot pin passing through it. The ends of this pivot pin are received in a component which defines a bearing having a stirrup-shaped profile. This bearing is carried on the intermediate plate of the starter frame. The operations of assembling and fitting the actuating lever, so that it can undergo its pivoting movement, are very complicated and expensive.
One example of a similar design is illustrated in the specification of French published patent application FR 2 567 586A, in which the pivot pin of the actuating lever is again mounted in a component which defines a bearing and which is carried on the intermediate flange or plate. In addition, designs are known in which the casing of the electromagnetic actuator, and that of the electric motor, are secured directly by screw fasteners on to the starter nose, with the articulating member of the actuating lever being itself fixed between the casings of the electromagnetic actuator and of the electric motor.